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3 Blackwell_IGARSS11_2860_MO3.T04.3.pptx
1. NPP ATMS Prelaunch Performance Assessment and Sensor Data Record Validation W. J. Blackwell, L. Chidester (SDL), C. Cull, E. J. Kim (NASA GSFC), R. V. Leslie, C.-H. Lyu (NASA GSFC), T. Mo (NOAA STAR), and I. Osaretin IGARSS July 25, 2011 This work was sponsored by the National Oceanographic and Atmospheric Administration under Air Force Contract FA8721-05-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the United States Government.
2. Outline ATMS Overview Background and development Performance Prelaunch testing Antenna Radiometric TVAC Post-launch validationof sensor/product performance Planning/schedule/objectives Tasks Summary
9. Advanced Technology Microwave Sounder (ATMS) ATMS is a 22 channel MW sounder Frequencies range from 23-183 GHz Total-power, two-point external calibration Continuous cross-track scanning, with torque & momentum compensation Orbits: 833 km (JPSS); 824 km (NPP); sun-synchronous Thermal control by spacecraft cold plate Contractor: Northrop Grumman Electronics Systems (NGES) 70 cm
10. ATMS Development ATMS NPP unit (“F1") developed by NASA/Goddard ATMS NPP unit delivered in 2005 ATMS JPSS-1 unit (“F2”) currently in development (antenna and TVACtesting in 2011/12, delivery in 2012) Principal challenges/advantages: Reduced size/power relative to AMSU Scan drive mechanism MMIC technology Improved spatial coverage (no gaps between swaths) Nyquist spatial sampling of temperature bands (improved information content relative to AMSU-A)
25. Atmospheric Transmission at Microwave Wavelengths ATMS channels The frequency dependence of atmospheric absorption allows different altitudes to be sensed by spacing channels along absorption lines
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27. Spatial Differences: ATMS vs. AMSU/MHS Beamwidth (degrees) Spatial sampling ATMS scan period: 8/3 sec; AMSU-A scan period: 8 sec ATMS measures 96 footprints per scan (30/90 for AMSU-A/B)
29. ATMS Data Products 1FOV = ATMS “Field of View”; FOR = CrIMSS “Field of Regard” RDR, TDR, SDR, and EDR products will be available via CLASS
30. Outline ATMS Overview Background and development Performance Prelaunch testing Antenna Radiometric TVAC Post-launch validationof sensor/product performance Planning/schedule/objectives Tasks Summary
31. ATMS Pre-Launch Testing Essential for two objectives: Ensure sensor meets performance specifications Ensure calibration parameters that are needed for SDR processing are adequately and accurately defined PFM testing revealed several issues that will require calibration corrections in the SDR: Non-linearity (temperature-dependent for 31.4-GHz channel) Cross-polarization (sometimes 10X higher than AMSU) Antenna beam spillover from secondary parabolic reflector approaching 2% for some channels A variety of prelaunch testing is performed to assess performance and reliability EMI/EMC - anechoic chamber for both emitted and susceptible measurements Mechanical – mass, CG, vibration, & torque on various fixtures Radiometric – thermal vacuum (TVac) testing Antenna – Compact Antenna Test Range (CATR)
32. Compact Antenna Range Testing Compact Antenna Test Range RF source illuminates the Antenna Under Test (AUT), i.e., ATMS antenna subsystem Uses a parabolic reflector to collimate the electromagnetic radiation to illuminate the AUT in the far-field region AUT is attached to a positioner to rotate the AUT into the proper orientation Test measures the power received by the AUT compared to a standard antenna with a known antenna gain pattern Specifications verified: Beam pointing accuracy Beamwidth Beam efficiency Earth intercept
37. ATMS Post-Launch Calibration/Validation in a Nutshell Post-launch is Cal/Val has four phases: Activation, Checkout, Intensive Cal/Val, and Long-term Trending Tasks within the phases can be categorized: Sensor Evaluation: interference, performance evaluation, etc. TDR/SDR Verification: geolocation, accuracy, etc. SDR Algorithm Tunable Parameters: bias correction, space view sector, etc. Activation Phase: Sensor is turned on and a sensor functional evaluation is performed; ATMS is collecting science data Checkout Phase: Performance evaluation and RFI evaluations Intensive Cal/Val: Verification of SDR attributes such as geolocation, resampling, brightness temperature accuracy (Simultaneous Nadir Overpass, Double Difference, radiosondes/NWP simulations, aircraft verification campaigns), and satellite maneuvers
38. ATMS On-Orbit FOV Characterization Spacecraft maneuvers (constant pitch up or roll, for example) could be used to sweep antenna beam across vicarious calibration sources Moon (probably too weak/broad for pattern assessment) Earth’s limb (requires atmospheric characterization) Focus of today’s presentation Land/sea boundary (good for verification of geolocation) With knowledge of the atmospheric state, the antenna pattern can be recovered with deconvolution techniques Objectives of this study - quantitatively assess: The benefits of various maneuvers How accurately can the pattern be recovered? The limitations of this approach How much roll/pitch is needed for an adequate measurement? The error sources and their impact
39. TB’s Across Earth/Space Transition LIMB (STANDARD ATMOSPHERE) SURFACE BEYOND STANDARD ATMOSPHERE 62.17°
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42. Evaluate key EDR algorithmsINSTRUMENTS: NAST-I & NAST-M NAST- I: IR Interferometer Sounder NAST- M: Microwave Sounder 5 Bands: 23/31 (to be added), 54, 118, 183, 425 GHz ~100km NAST- M Cruising altitude: ~17-20 km Cross-track scanning: - 65º to 65º
44. Summary All key radiometric requirements were satisfied Radiometric accuracy exceeds 1K Radiometric sensitivity exceeds requirements Similar to AMSU for similar effective footprint sizes Linearity performance generally exceeds AMSU Antenna pattern testing indicates good performance Opportunity for spacecraft maneuvers allows improved characterization of ATMS spatial response function Post-launch cal/val plans are well defined Readiness exercises ongoing Areas to watch have been illuminated during prelaunch testing
46. Utility of Aircraft Underflights What do aircraft measurements provide that we cannot get anywhere else? Why not just compare to radiosondes or NWP? Direct radiance comparisons Removes modeling errors Mobile platform High spatial & temporal coincidence achievable Spectral response matched to satellite With additional radiometers for calibration Higher spatial resolution than satellite Additional instrumentation deployed Coincident video data Dropsondes Example video image Solar glint Ocean Clouds
47. Synergistic Use of MW+IR:Infrared Provides High Spatial Resolution For example, CrIS provides 15km horizontal and 1km vertical resolution
48. Passive Microwave Measurements Provide Low Spatial Resolution, but Penetrate Clouds For example, ATMS provides 33km horizontal and 3km vertical resolution
I will begin with an overview of the ATMS sensor and move onto to validation plans once the NPP satellite launches. The talk concludes with a discussion of applications of the ATMS data.
Shown is a picture of the NPP satellite with the five sensors installed.
An overview of the ATMS sensor.
History of the ATMS development.
The principal challenge of the ATMS development was the consolidation of three sensors (AMSU-A, AMSU-B, and MHS) into a single sensor with a longer lifetime requirement.
The frequency dependence of atmospheric absorption allows different altitudes to be sensed by spacing channels along absorption lines
An overview of the principal differences between ATMS and AMSU.
Spatial attributes of ATMS and AMSU.
These data products will be derived from ATMS observations.
I will begin with an overview of the ATMS sensor and move onto to validation plans once the NPP satellite launches. The talk concludes with a discussion of applications of the ATMS data.
The ATMS PFM has completed its characterization and satellite-level testing is mainly to confirm performance after five years. The pre-launch characterization included antenna pattern characterization using a Compact Antenna Test Range (CATR), susceptibility to radio frequency interference, and calibration accuracy and RMS analysis in a thermal vacuum chamber using precision external calibration targets. Listed in the second bullet were some results of the characterization. The sensor had larger than expected non-linearity and required a waiver, but it generally exceeds AMSU. A temperature-dependent NL correction factor was derived from Thermal-Vacuum data. The EDR performance is still being evaluated, but we’re hopeful they can be met with some on-orbit calibration that I’ll discuss more later in the presentation.
I will begin with an overview of the ATMS sensor and move onto to validation plans once the NPP satellite launches. The talk concludes with a discussion of applications of the ATMS data.
Post-launch cal/val has an extensive history and is becoming increasingly sophisticated. The ATMS SDR validation plan includes Simultaneous Nadir Overpass; Double Difference; radiance comparisons using NWP, radiosondes, and CrIS radiances; aircraft campaigns; satellite maneuvers, etc. Another tool will be an end-to-end ATMS/CrIMSS system error model/budget that will model the system from RDRs to EDRs and will use information derived from sensor thermal-vacuum data, radiative transfer, heritage sensors, and eventually ATMS data. The rest of this presentations will discuss the ATMS proxy data that uses AMSU/MHS, aircraft validation, and on-orbit spacecraft maneuvers.
At a very abstract level, here are the objectives and primary components of a successful cal/val campaign. I will touch on most of these during the presentation.
ATMS observations will be used to improve forecast accuracy. The microwave instruments have the largest positive impact on forecast accuracy.
Recent work is shown where ATMS observations are used to estimate the intensity of precipitation.
